Through phase transformation kinetic analysis and experimental observation,the δ/γtransformation occurring in the non-equilibrium peritectic Fe-4.33at.%Ni alloys was systematically investigated.According to JMA solid-state transformation ki-netic theory,the Time-Temperature-Transformation(TTT)curves of the δ/γtrans-formation in peritectic Fe-Ni alloy were calculated.On this basis,the physical cor-relation between the δ/γtransformation and the initial undercooling of melt(T)was elucidated.The results indicate that the change of T can alter not only the overall δ/γtransformation pathways but also the transformation fraction with re-spect to each transformation mechanism.
A solute trapping model is developed based on a so-called solute drag treatment.By adopting a basic approach of phase-field models,and defining the free energy density in the interfacial region,a suitable interface shape function is introduced to derive the current model,in which the equilibrium and non-equilibrium interface behaviours can be described using a dimensionless parameter L (i.e.an important parameter in the present interface shape function).When applying the current model to Si-9%As (molar fraction) alloy with L=0.5,a good prediction of the steeper profile for high interface velocity,which is analogous to that using a phase-field model of DANILOV and NESLTER,has been obtained.
Pd81Si19 amorphous alloys were prepared by combination methods of melt spinning and B2O3 flux treatment. A compari- son between the ribbons prepared from the fluxed ingots and the non-fluxed ones has been carried out. The result reveals that after fluxing treatment the glass transition temperature of the as-prepared glassy ribbons is reduced while the initial crystallization tem- perature is enhanced. It results in that the supercooled liquid region (defined as the difference between the initial crystallization tem- perature and the glass transition temperature) of the glassy alloy treated with fluxing technology has been increased from 31 to 42 K. This shows that fluxing technique can enhance the glass forming ability (GFA) of the binary alloy and improve the thermal stability of supercooled liquid of the glassy alloy.
Na Chen, Kefu Yao, and Fang Ruan Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China.
